New York: The UN Security Council held a closed-door meeting to discuss the situation in Syria following a massacre of more than 100 civilians in the western town of Houla.

German Ambassador to UN Peter Wittig said ahead of the talks that the Security Council was planning to consider a possibility of sending more UN monitors to Syria to reinforce the current 300-strong mission.

It would also discuss opportunities to influence the Syrian regime with the aim of ending violence in the country torn by a severe political crisis.

He also said it was a lack of UN action on Syria that has led to the aggravation of the 15-month-old crisis.

The Security Council condemned "in the strongest terms" the Houla massacre, in which over 100 people, including some 50 children and 30 women, were killed in cold blood last week.

UN peacekeeping chief Herve Ladsous said there was "strong suspicion" that militia loyal to Syrian President Bashar al-Assad carried out the massacre.

He said the Syrian government was responsible for part of the deaths in Houla, as monitors confirmed that artillery and tank shells -- which only government forces have -- had been fired at Houla`s residential areas.

On Wednesday, UN monitors said they had discovered 13 bound corpses in eastern Syria, many of them apparently shot in the head from a short distance.

The Syrian government has denied its involvement in the killings, blaming them on "armed terrorists".